The present invention relates to a method for fabricating a nonvolatile memory device, and more particularly, to a method for fabricating a NAND-type flash memory device in which a plurality of memory cells are connected in series to form a unit string.
A NAND-type flash memory device is a nonvolatile memory device in which a plurality of memory cells is connected in series to form a unit string in order for realizing a high integration of the memory device. The application fields of the NAND-type flash memory device have expanded to the extent that the NAND-type flash memory replaces a memory stick, a universal serial bus (USB) driver, and a hard disk.
The NAND-type flash memory device is very vulnerable to interference between adjacent cells because a plurality of memory cells is connected in series to form the unit string. A wing spacer technique has been proposed to improve the interference effect in the fabrication of the NAND-type flash memory device using an advanced self aligned-shallow trench isolation (ASA-STI) process. This technique uses a conductive control gate to shield the adjacent floating gates from each other.
In the typical fabricating process of the NAND-type flash memory device using the wing spacer technique, however, an etching process for forming wing spacers is additionally performed and foreign particles are produced. Therefore, if a dielectric layer is formed through a subsequent process, the foreign particles exist within the dielectric layer, leading to degradation of device characteristics.